ELK is the acronym for three open source projects: ElasticSearch, Logstash, Kibana. Elasticsearch is a search and analytics engine. Logstash is a server-side data processing pipeline that ingest data from multiple sources simultaneously, transform it and then sends it to Elasticsearch. Kibana lets users visualize data with charts and graphs using collected data in Elasticsearch.
https://www.elastic.co/what-is/elk-stack
Requirements for _meas_node
Each Elasticsearch node requires 1GB of RAM to run the 3-node cluster. Make sure to create _meas_node with enough RAM. By default, the _meas_node is created with 2 CPU cores, 100GB storage and 8GB RAM.